Systems and methods for opening and starting a vehicle by means of a mobile terminal device are known from the prior art and are marketed, for example, under the brand name Keyless Go in order to make the handling of vehicle fleets or car sharing offerings more efficient. A digital vehicle key of the vehicle is normally integrated into the mobile terminal device. The digital key can be transmitted via a mobile radiocommunication network onto the mobile terminal device of the car-sharing user. Following a data exchange between the mobile terminal device of the user and the vehicle, for example via a near-field communication connection, the vehicle can be opened and can be started by the user.
However, despite the much-vaunted security, the aforementioned systems and methods have various security shortcomings. Accordingly, cases of misuse have increasingly been reported in recent years in which unauthorized parties have opened or even stolen the vehicle.